What is knee joint replacement?

Knee joint replacement is a procedure that involves replacing an injured or ailing knee with an artificial joint, or prosthesis.

The prosthesis is made of metal alloys, plastics, and polymers. It mimics the function of a knee. According to the American Academy of Orthopaedic Surgeons (AAOS), replacement knees can fit your needs and specifications. When selecting a prosthetic knee, your doctor will take into account your:

  • age
  • weight
  • activity level
  • overall health

The procedure to remove your old knee and replace it with a prosthesis usually takes less than two hours, but recovery and rehabilitation can last months.

Another name for this procedure is knee arthroplasty. Knee replacements are a very common surgery. The AAOS notes that more than 600,000 knee replacements occur every year in the United States.

Damage from arthritis is the most common reason for knee joint replacement. This includes both osteoarthritis and rheumatoid arthritis.

Doctors usually only recommend knee replacement after other, less invasive treatments have failed. First-line treatment options include:

  • weight loss
  • medications
  • physical therapy
  • assistive devices, such as a cane or a knee brace

Key factors in determining if you’re a good candidate for knee joint replacement include:

  • how much your knee pain interferes with daily activities, such as walking or climbing stairs
  • if your knee is deformed, bows, or “blows out” regularly
  • your age
  • your overall health

Knee surgery is a typical treatment for people over the age of 55. Younger people who have their knees replaced may outlive their artificial knees and may need a revision.

Doctors evaluate each candidate for knee replacement surgery on an individual basis.

Before surgery, your doctor will assess your overall health and anesthesia risks. This evaluation will include:

  • a full medical history
  • a physical examination
  • blood tests
  • X-rays
  • other imaging tests

Your doctor will ask you for your complete medical history, including any prior surgeries and ongoing health conditions you have. Tell your doctor about any medication you’re taking including over-the-counter medicines and nutritional supplements. You may have to stop taking some or all of them before your surgery.

Also, tell your doctor if you’ve ever had an allergic reaction to anesthesia. Your doctor will review your anesthesia options based on your preferences and what they think is appropriate for your situation. This could include general anesthesia, which means you’re asleep during surgery. Or, you may receive anesthesia in your spine, which leaves you awake but pain-free from the waist down.

Your doctor will give your surgeon the results of your medical evaluation, medical history, and your anesthesia choice.

You can expect to walk with the aid of crutches or a walker for several weeks. Before surgery, you should prepare your home to accommodate your recovery:

  • You may need to install handles in showers and around the toilet.
  • It’s good to have a chair and footrest available so you can elevate your leg.
  • If possible, keep your living space on the first floor if you have a multistory house.

Your doctor and surgical team will give you full instructions on how to best prepare for surgery. It’s important to follow those instructions as closely as possible.

When it’s time for your surgery, you’ll change into a hospital gown and get an IV to provide you with fluids and nutrients during the surgery. Just before surgery, you’ll receive anesthesia.

During the procedure, which lasts between one and two hours, your surgeon will make a long surgical cut above your knee. With the skin and muscle pulled back, they’ll cut away damaged cartilage and bone.

They’ll affix the new knee joint to your femur, or thighbone, and tibia, which is the main bone in your lower leg. They’ll do this using specialized cement, pins, and screws. Afterward, your surgeon will close the incision wound with stitches and apply a bandage.

You’ll recover from the surgery in a special recovery room where a team can monitor your vital signs.

After surgery, your leg will feel stiff. You’ll experience some pain. Receiving painkillers through your vein, or intravenously, can help manage this pain. You may receive long-acting local anesthetics at the time of surgery or possibly a nerve block to help with postoperative pain. You’ll also receive medication to prevent your blood from clotting.

Most people begin physical therapy the day of surgery or day after their surgery to promote blood flow to the tissues around the new knee. Your surgeon may recommend using a continuous passive-motion machine. This is a special brace-like device that continuously moves your knee in a gentle bending motion.

Your surgeon will let you know when it’s best to leave the hospital. This is based on the results of the surgery and your condition.

Following your surgery, you’ll undergo considerable physical therapy. Your surgeon and physical therapy team will design a program that’s right for you.

Every medical procedure carries the risk of bleeding, blood clots, and infection. Your doctor will explain these risks and what you can do to minimize them. The AAOS states that less than 2 percent of the more than 600,000 people who have total knee replacements each year in the United States have serious complications.

Complications associated with knee replacement surgery include:

  • the artificial knee wearing out over time
  • bleeding
  • blood clots in the leg or lungs
  • breathing problems caused by the anesthesia
  • a heart attack
  • knee stiffness
  • nerve damage in the knee
  • a stroke

Contact your doctor immediately if you experience the following symptoms:

  • chills
  • drainage from your surgical scar
  • a fever over 100°F (37.8°C)
  • increasing pain, redness, swelling, and tenderness in the knee

Infection is an ongoing concern for people who receive artificial joints. As bacteria and other contaminants regularly flow through your blood, they can infect your artificial knee. If you have a knee infection, your doctor may have to remove part of or the whole artificial knee to treat the infection before they can implant one again.